The present invention generally relates to medical instruments. More particularly, the present invention relates thoracentesis needle devices which are used in the removal of fluid from the pleural cavity and which prevent air entry into the pleural cavity during use. Specifically, the invention relates to a sheath catheter assembly for a thoracentesis needle.
The thoracentesis procedure involves incising through the chest wall, and inserting a tube or catheter through the chest wall and into the pleural cavity. By providing a negative pressure at the proximal end of the catheter, intrathoracic fluid such as blood, puss, air, and other secretions are removed from the pleural cavity. While removal of the intrathoracic fluid is desirable, at the same time it is imperative for a negative pressure to be maintained in the pleural cavity in order to permit the lungs to remain expanded such that breathing can continue. In order to maintain a negative pressure in the pleural cavity, care must be taken to avoid communication between the pleural cavity and atmospheric pressure, as a passage of air from outside the body into the pleural cavity can collapse the lung; a medical condition known as pneumothorax.
A common manner of conducting a thoracentesis procedure is to make a chest wall incision using a needle. In introducing the needle into the pleural cavity, care must be taken to avoid pushing the needle too far and puncturing the lung, as air from the lung space could escape into the pleural cavity and result in a lung collapse. In such cases it is actually possible to produce a pressure within the pleural cavity which is greater than atmospheric pressure, and cardiac compromise is a possible consequence.
A thoracentesis device which purportedly reduces possibility of lung puncture and reduces pneumothorax due to entry of air into the pleural cavity is proposed in U.S. Pat. No. 4,447,235 to Clarke. The proposed device includes a needle having a drainage opening which extends through a catheter and through an elongated conduit connected to the catheter. The elongated conduit is provided with an elastomeric seal and a manual valve. The elastomeric seal, which is punctured by the needle when the needle ia inserted through the elongated conduit and catheter, prevents air leakage into the pleural cavity by sealing around the needle and resealing when the needle is removed. The manual valve, when moved, permits the elongate conduit to open to a side conduit when the needle is removed, thereby permitting long term drainage of the pleural cavity. In the Clarke patent, the removal of the needle is what reduces the possibility of lung puncture.
In addition to the device proposed in the Clarke patent, devices and procedures are set forth in U.S. Pat. Nos. 4,784,156, 4,832,044, 4,840,184, and 4,844,087 to Garg. In the Garg patents, a manual in-line valve is provided, and upon retraction of the needle past the valve, the valve is turned such that entry of air into the pleural cavity is prevented.
While the prior art patents represent advances in the art, it should be appreciated that with the prior art devices, it is still relatively easy for even a skilled surgeon to puncture the lung by pushing the needle just slightly too far into the pleural cavity. In fact, even if the needle is in the pleural cavity for a short period of time, should the patient move or cough, or even take a deep breath, it is possible for the needle to puncture the lung. In addition, with the manual valve structures of the prior art, should the attending surgeon forget to properly move the valve into the desired positions at certain times, undesirable results may be obtained.
Also long known in the art are needles called "Veress" or "Veress-type" needles. Veress needles are needles with an outer needle having a sharp distal end and an inner probe which extends through the outer needle with the probe having a blunt distal end. In Veress needles, the inner probe is biased to force the blunt distal end of the probe beyond the sharp distal end of the outer needle. However, when the blunt distal end of the probe encounters dense material, the probe is forced backward and the sharp end of the needle is presented so that it can puncture the dense material. Veress needles are used in the art almost exclusively for insufflation (injection of carbon dioxide) of the abdomen during laparoscopy procedures, and Veress needles with manual shut-off valves are known in the art. Veress needles have also been suggested for use in a thoracentesis procedure (See, Jenkins, Jr. Douglas, et al., "Veress Needle in the Pleural Space", Southern Medical Journal: Vol. 76, No. 11, pp. 1383-1395 (Nov. 1983)), although the techniques suggested therein in a test study have not gained popularity over the several years since they were reported and are not today used in common practice. Regardless of use, the Veress needle assemblies of the art have not before been modified for particular use in conjunction with withdrawal of fluid, and in particular withdrawal of fluid from the pleural cavity. Indeed, the Veress needle assemblies of the art have not been used with automatic check valves.
Parent application Ser. No. 07/860,447, discloses and claims a thoracentesis needle assembly which utilizes a Veress-type needle arrangement to overcome lung puncture problems as well as an automatic valve to prevent pneumothorax. In addition, the disclosed needle assembly may be used with a catheter such as the catheter disclosed by Clarke in U.S. Pat. No. 4,447,235. The catheter disclosed by Clarke, like the cannulae disclosed by Garg in U.S. Pat. Nos. 4,784,156, 4,832,044, 4,840,184, and 4,844,087, provides a manual valve in line with the needle assembly, and with a hollow cylindrical stopcock rotatably fitted with an external lever. Moving the external lever in one direction allows the thoracentesis needle to pass into the catheter, and moving the external lever in the other direction after the thoracentesis needle is removed prevents air from entering the catheter and directs fluid flow to a drainage attachment or the like. The chief disadvantages of the Clarke arrangement are that a valve which can be subject to clogging is used in the flow line, and that the in-line valve must be of exact design to permit needle insertion. Moreover, the attending surgeon must remember to set the valve to the correct position at the correct time. When the needle is inserted in the catheter, the valve must be placed in one position wherein the needle passes through the valve. After the needle is withdrawn from the catheter, the valve must be manually turned to a second position to redirect fluid flow from the catheter and block the needle passage. While Clarke provides an elastomeric seal in addition to the manual valve to prevent air from entering the catheter after the needle is withdrawn, this seal is merely a piece of elastomeric material which is pierced when the needle is inserted. Theoretically, when the needle is withdrawn, the elastomeric material will contract and close the opening which was made when the needle pierced it. While this solution sounds reasonable, it assumes that a needle of very small diameter is used. In practice, however, if a Veress-type needle is used, a piece of the elastomeric seal can be cut off by the needle and embedded inside the hollow of the needle. This presents two problems: first, a piece of elastomeric material will be delivered into the pleural cavity, and second, the resealing of the elastomeric seal is severely compromised since a piece of it is now missing.